It's a Monday morning in Cambridge and Richard Evans shuffles out of the porter's lodge at Gonville & Caius College trailing a large suitcase behind him. "Been somewhere nice for the weekend?" I ask. Evans looks confused for a moment. "I haven't been anywhere," he eventually replies. "I've got someone flying in from the US to research the Irving trial and these are some of the documents."

The emphasis here should be on the "some". In the five years between 1995 and 2000 the standard bibliography of works on the Nazis increased from 25,000 to 37,000: the figure has no doubt grown still further since then, and Evans himself has to take his fair share of the credit. Or blame.

As professor of modern history at Cambridge and one of the country's leading experts on the Nazi period, he's generated several shelves of archives on his own - most notably as the star defence witness for Penguin books in the David Irving Holocaust denial libel trial in 2000. Indeed, the story of the publication of his book about the trial, Telling Lies about Hitler, produced its only mini sub-archive as first Heinemann, then Granta and finally Profile declined to publish it for various legal reasons, before Verso stepped in. "You can read all about it in Private Eye," he adds, a little testily.

And this month sees yet another addition to the Nazi canon as Evans publishes The Coming of the Third Reich, the first in a projected trilogy on Nazi Germany. So what more can be said on the subject? "It's precisely because the literature is so enormous, that I felt there was a need for a major overview and synthesis of the material," he argues. "Research has gone in three phases: in the 50s and 60s West German historians tried to understand how fascism arose from the Weimar democracy, then in the 70s and 80s historians worked on the structures of the Reich between 1933-39, and since the 90s the main focus has been the war and the Holocaust."

Evans's books will dovetail nicely with these three periods. The Coming of the Third Reich steers a comfortable middle-ground between the determinists, such as AJP Taylor, who reckon that Nazism was a historical inevitability for Germany ever since Luther drew his first breath and the only real surprise is that it didn't happen earlier, and those who see it as an aberration with no deep roots in German culture.

"The trouble with history is that you study it in reverse, so everything can appear to have an immediate cause and effect," he points out. "So while the driving force of Nazism can be seen as far back as Bismarck with the marginalisation of the Catholics and socialists together with the emergence of a nationalism based on Social Darwinism and eugenics, you can never say it was an inevitability. If German unification had taken place in a less authoritarian way, if the first world war had not taken place, if the Weimar constitution had been worded differently, if the Depression had not put one-third of the workforce out of a job and had Hindenburg not written off the Nazis as politically naive and compliant, then German history of the 30s and 40s might have looked very different."

Evans also has an implicit pop at modern academics, such as Michael Burleigh, for what he sees as a new trend for overwriting history as a series of moral judgments. "Of course a historian cannot avoid expressing certain values," he says. "It's clear from my own work that I believe in a multicultural democracy, but to go from that position to say someone is morally good or bad is either unnecessary or simplistic. The principal task of history is to explain and interpret, not to issue moral judgments."

In print, that is. For in his work on the government's spoliations committee that was set up three years ago to determine people's right to compensation for art works appropriated by the Nazis, Evans is only too happy to make moral judgments. Indeed moral judgments are the only ones available as the time limit for all legal claims has long since passed. He admits it's a long and difficult process and so far the committee has only made one award, a payment of £125,000 to a family who were forced to sell a painting of Hampton Court by Jan Griffier the Elder - which now hangs in the Tate - for next to nothing. A half dozen or so other cases remain pending.

Evans sees no inconsistency between these two positions, but then confidence has always been one of his strongest suits. Towards the end of the 90s he took on the postmodernists and post-structuralists who were predicting the end of history as an academic discipline in his book In Defence of History. In it, he fought off suggestions that all history was a matter of a reader's interpretation, by asserting the right of the author to define the text. You get the feeling he bit off a little more than expected, as the book was attacked on two fronts - by the conservatives for being too quiescent to the wishy-washy liberals and by the postmodernists for being too reactionary.

"It was all good-natured stuff, really," he laughs. "The really nasty spats died out when dons stopped living in college, as the disputes tended to be more marital than academic."

Still, as ever, he came out fighting, quickly adding a 50-page afterword, reiterating and refining his position, for the paperback edition and, though he admits he wasn't as clear as he might have been in the original, he reckons he more than won the argument. "The postmodernists rather proved my point by complaining I had misrepresented what they had written and, far from dying out, history has gone from strength to strength."

Not that Evans believes all is well within the discipline. "When I came to Oxford in the late 60s you had to have studied Latin and at least one other modern language," he says. "Now there is no language requirement, and I worry for the state of British history if none of our academics of the future is able to study foreign sources. Already my PhD students are predominantly German as they are bilingual."

As professor of modern history at Cambridge for the last six years, and at Birkbeck for nine years before that, Evans acknowledges it is a long time since he came into contact with any average undergraduates. But he does feel that with history no longer compulsory at GCSE and with the A-level syllabus - in many people's view - extremely limited, many students have huge knowledge gaps. "It doesn't work to my advantage at all," he smiles. "Most of those who come up to Cambridge are sick and tired of learning about the Nazis and want to start afresh. I've only got four undergraduate students at the moment."

So could the present-day fixation with the Nazis be on the wane? Evans's interest grew out of his upbringing in Epping Forest on the outskirts of London - from seeing the bombed-out rubble of the East End at first hand and witnessing the growth of racism and the National Front in the mid-60s and the failed American imperialism in Vietnam. He is well aware that today's students will have their own agenda.

"You can't predict what will motivate people in years to come," he says. "It will depend on what situation we find ourselves in and what areas of research open up. One of the reasons why there was a sudden explosion of interest in the Nazis in the 90s was due to the opening up of the former Soviet bloc countries. Overnight, huge archives became available."

So is there anything left for us still to discover? "Oh yes," he enthuses. "We still know very little about the concentration camps - especially the satellite camps, the German economy and the criminal justice system. I've plenty of ideas if anyone is stuck for a PhD topic."

Looks like there's still life left in them thar Nazis.

The CV

Name: Richard John Evans

Age: 56

Job: Professor of modern history, Cambridge University, and fellow of Gonville and Caius College.

Before that: Lecturer in history, Stirling University; professor of European history, University of East Anglia; professor of history, Birkbeck College London.

Other appearances: Expert defence witness in the David Irving Holocaust denial libel trial; member of the government's Spoliations Committee.